The components of the quantum Fisher information matrix are defined as [1]}
\( {\cal F}_{\theta _{\mu }\theta _{\nu }}\left(\rho _{\theta }\right):=\frac{1}{2}{\rm Tr}\left(\rho _{\theta }\left\lbrace \hat{L}_{\theta _{\mu }},\hat{L}_{\theta _{\nu }} \right\rbrace \right),\) 
